1. Technical Field
The present invention relates to a fuel cell system, and more particularly to a fuel cell system including a fluid circulating device which is disposed in a fluid passage connected to a fuel cell main body.
2. Related Art
An advantage of installing batteries comprised of fuel cells on in vehicles is that their impact on the environment is relatively small. Fuel cells generate required electric power by, for example, reacting a fuel gas such as hydrogen supplied to an anode side of a fuel cell with an oxidizing gas such as air supplied to a cathode side, causing a reaction through an electrolyte membrane. Because heat is generated as a result of such a reaction, a coolant such as cooling water is circulated through the fuel cell stack, so that a radiator or the like may be used to cool the stack.
Thus, such a fuel cell system comprises a fuel cell stack and a fuel gas passage, an oxidizing gas passage, a cooling water passage, and the like connected thereto. Typically, the fluid passages are each provided with one or both of a valve for controlling fluid flow, or a fluid circulating device such as a drive device, a pump, or a compressor.
For example, JP-A 2005-251576 (Patent Document 1) discloses a fuel cell system comprising an atomizer having an ultrasonic transducer for atomizing the water in an air exhaust system, in which a gate valve is operated to switch between a bypass supply pipe and a bypass exhaust pipe in order to provide a bypass state for a humidifier, and an air compressor is driven to scavenge.
If such a fluid circulating device does not operate, the operation of the fuel cell system may be hindered; various measures have been employed to deal with failure of such devices. For example, JP-A 2006-310209 (Patent Document 2) discloses a fuel cell system in which, if electric power is not supplied from a storage battery which has discharged after a long period of non use, the storage battery is recharged by external energy from a manual power generator or the like, thereby the fuel cell battery is activated.
Patent Publication JP-A 2001-336803 (Patent Document 3) does not directly relate to fuel cells, but discloses a temperature-control device in which an ON-OFF valve within a coolant circulating passage may be fixed in a closed state if it is not used or put in a stopped state for a long period. This'publication discloses that the ON-OFF valve is forcibly opened when the operation is stopped for a predetermined period, and a pump is used to forcibly circulate remaining coolant.